Performance of Digital SQUID Gradiometer for MCG Measurement Under Different Shielding Conditions in a Variety of Noisy Environments

In this work, two HTS YBCO rf SQUIDs are used to form a gradiometer without electronic subtraction and digital data processing is applied to cancel the environmental noise. With healthy volunteers as measuring subjects, MCG recordings of various signal-to-noise-ratio SNR are obtained under different shielding conditions in environments of different noise components and characteristics. To extract the signal, data processing procedures based on adaptive filtering, wavelet transform and independent component analysis are studied and utilized to raise the SNR in each measurement respectively. The performances of these numerical methods are evaluated and compared. The result shows that using appropriate data processing methods one can get acceptable signal quality in comparatively more noisy environment with weak shielding.